This new waterfront Belvedere Island mansion goes up for auction on Dec. 30 at a starting bid of $25 million.

Photo: Courtesy Olivia Hsu Decker

This new waterfront Belvedere Island mansion goes up for auction on...

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Villa Belvedere, a waterfront home in Belvedere, is listed for $39 million and was the 2012 Marin Designer Showcase home. It looks out onto San Francisco and the Golden Gate Bridge and is nearly 10,000 square feet and was designed by architect Sandy Walker.

Photo: Courtesy Olivia Hsu Decker

Villa Belvedere, a waterfront home in Belvedere, is listed for $39...

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Villa Belvedere, a waterfront home in Belvedere, is listed for $39 million and was the 2012 Marin Designer Showcase home. It looks out onto San Francisco and the Golden Gate Bridge and is nearly 10,000 square feet and was designed by architect Sandy Walker.

Photo: Courtesy Olivia Hsu Decker

Villa Belvedere, a waterfront home in Belvedere, is listed for $39...

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Villa Belvedere, a waterfront home in Belvedere, is listed for $39 million and was the 2012 Marin Designer Showcase home. It looks out onto San Francisco and the Golden Gate Bridge and is nearly 10,000 square feet and was designed by architect Sandy Walker.

Photo: Courtesy Olivia Hsu Decker

Villa Belvedere, a waterfront home in Belvedere, is listed for $39...

Image 5 of 13

Villa Belvedere, a waterfront home in Belvedere, is listed for $39 million and was the 2012 Marin Designer Showcase home. It looks out onto San Francisco and the Golden Gate Bridge and is nearly 10,000 square feet and was designed by architect Sandy Walker.

Photo: Courtesy Olivia Hsu Decker

Villa Belvedere, a waterfront home in Belvedere, is listed for $39...

Image 6 of 13

Villa Belvedere, a waterfront home in Belvedere, is listed for $39 million and was the 2012 Marin Designer Showcase home. It looks out onto San Francisco and the Golden Gate Bridge and is nearly 10,000 square feet and was designed by architect Sandy Walker.

Photo: Courtesy Olivia Hsu Decker

Villa Belvedere, a waterfront home in Belvedere, is listed for $39...

Image 7 of 13

Villa Belvedere, a waterfront home in Belvedere, is listed for $39 million and was the 2012 Marin Designer Showcase home. It looks out onto San Francisco and the Golden Gate Bridge and is nearly 10,000 square feet and was designed by architect Sandy Walker.

Photo: Courtesy Olivia Hsu Decker

Villa Belvedere, a waterfront home in Belvedere, is listed for $39...

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The kitchen at Villa Belvedere.

Photo: Courtesy Olivia Hsu Decker

The kitchen at Villa Belvedere.

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The dining area with a view of the Golden Gate Bridge.

Photo: Courtesy Olivia Hsu Decker

The dining area with a view of the Golden Gate Bridge.

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The dining area seen from the terrace at Villa Belvedere.

Photo: Courtesy Olivia Hsu Decker

The dining area seen from the terrace at Villa Belvedere.

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Villa Belvedere, a waterfront home in Belvedere, is listed for $39 million and was the 2012 Marin Designer Showcase home. It looks out onto San Francisco and the Golden Gate Bridge and is nearly 10,000 square feet and was designed by architect Sandy Walker.

Photo: Matt McCourtney

Villa Belvedere, a waterfront home in Belvedere, is listed for $39...

Image 12 of 13

Villa Belvedere, a waterfront home in Belvedere, is listed for $39 million and was the 2012 Marin Designer Showcase home. It looks out onto San Francisco and the Golden Gate Bridge and is nearly 10,000 square feet and was designed by architect Sandy Walker.

Photo: Courtesy Olivia Hsu Decker

Villa Belvedere, a waterfront home in Belvedere, is listed for $39...

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Among the home's amenities - views, sauna - it has a temperature-controlled wine cellar.

One of the most expensive properties on the Bay Area market will be auctioned off to the highest bidder on Dec. 30, an unusual move for a luxury home not involved in a foreclosure.

A mere $25 million bid will put you in the running for a brand-new Belvedere Island mansion in Marin County. And though there's no telling where the bidding might end, the property was previously listed for $35.88 million without attracting a buyer.

Since the developer spent around $34.5 million buying the 1.14-acre waterfront lot and building the 15,500-square-foot, seven-bedroom home, according to real estate agent Olivia Hsu Decker, the auction winner could well get a relative bargain - if anything that costs more than $25 million can be called a bargain.

Developer Jeff Paster said he decided to hold an auction because he wants to move on to other real estate projects.

"This is a way to set a level playing field and a deadline for the interested buyers to offer fair market value for the property. This is certainly not a distress sale," Paster said.

Setting a price

Paster has faced financial difficulties in completing the project, however, according to legal filings with the city of Belvedere, which reportedly fined him twice for not finishing the house within a two-year window. The delays were due to the credit crunch, according to an appeal filed by Paster's attorney.

Though often not a seller's first choice, auctions can help set a price for unique properties, which are difficult to value, said Mark L. Troen, chief operating officer at New York auction firm Sheldon Good & Co.

Rarefied ballpark

Completed early this year, the Belvedere mansion was first listed for $45 million, putting it in a price range where qualified buyers and comparable properties are few. Only one house has sold for more than that in the Bay Area, according to real estate researcher DataQuick - the $100 million Los Altos Hills mansion purchased last year by Russian billionaire Yuri Milner, reportedly the most ever paid for a single-family home.

There have been asking prices in this rarefied ballpark, but as far as actual sales in the past five years, the four next-highest prices paid in the Bay Area ranged from $23.5 million to $33 million, according to DataQuick. A mansion on Broadway in San Francisco closed escrow for $28.8 million earlier this week.

Paster said he will donate 1 percent of the sale price to charity - half to victims of Superstorm Sandy and half to the cause of the buyer's choice. Hsu Decker, of Decker Bullock Sotheby's International Realty, and auction consultant Guy Masters are also planning to donate 10 percent of their commissions, Paster said.

Eye-opening

Selling luxury homes that are not in foreclosure at auction seems to be an emerging trend, Troen said. Sheldon Good is on track to sell almost a dozen "super luxury" homes at seven-figure or eight-figure prices, after auctioning off only three in 2011, he said.

While some sellers might go to auction because their loans are coming due and they need to sell immediately, others are using auctions simply as a way to "recapitalize" now that the luxury market is coming back somewhat, Troen said.

"Most likely, many of them have already tried a conventional means and did not succeed," Troen said.

Even for tony Belvedere, the property is eye-popping, with nearly every room opening up to postcard views of the Golden Gate and Bay bridges, San Francisco, Alcatraz and the bay. A deep terrace running the full length of the house will provide the future owner with front-row seats for the 2013 America's Cup races, said Hsu Decker.

The house, designed by architect Sandy Walker, also has solar panels on the roof and iPads mounted on the walls that can be used to control the temperature, security and other systems.

Big price tag

And even for Belvedere, the price tag is eye-popping, too. At an open house on Sunday, a Maserati was parked near a sculpture in the motor court, and most folks strolling through and enjoying the view said they lived in Belvedere or Tiburon. Still, no one there said they would be bidding on the house.

"We didn't even bring our checkbook," joked Cheryl Haley, who came with her husband to show the place to a friend. Haley had already been to Villa Belvedere, as the seller calls it, twice, for the Marin Designers Showcase fundraiser in February, when each room was decorated by a different designer, and for a party commemorating the 75th anniversary of the Golden Gate Bridge in May.

"I just need my Google stock to come through," another viewer joked as he walked through the sun-drenched rooms.

Offers rejected

Private showings have been arranged for house hunters from overseas and for small groups of potentially qualified buyers, said Justin Fichelson, another agent with Decker Bullock Sotheby's International Realty.

"There are a lot of people looking at it, but because of the offers he turned down in the past, no one has written an offer. The only way to get the whole world to know he means business is to set an auction," she said.

For auction consultant Masters, who is staying in the mansion with his Cavalier King Charles spaniel, Maggie, through the auction day, the sale would be his first as an independent consultant specializing in "marketing non-distressed, prominent properties," as his website states.

Pricey property

The home known as Villa Belvedere is scheduled to go up for auction on Dec. 30. Here's a look at the property's vital statistics: